The invention relates to a locking and unlocking device for a card reader of the type in which the card is entered into the card reader through an entry slot and ejected by spring force. More specifically, the invention relates to a locking and unlocking device in which an at least partially closed hook of a locking element projects into the card entry slot in the quiescent condition, whereby the end of the card is hooked by the hook while the card is being read and the card may be removed from the entry slot by means of a key acting upon the locking element through a lever mechanism.
Numerous designs for these types of card readers are known. The card is normally placed on a longitudinally slideable entry tray and carried to an evaluating device. In order to read the card accurately, the card must be precisely positioned within the card reader while being read. This has been achieved through the action of a mechanical cam or by electromechanical means.
German Offenlegungsschrift P No. 33 43 727 shows a card reader in which the card receptor is a drawer that is insertable into an opening in a telephone station, and that is carried to, and is held within, a trough area in the bottom of the unit. In the inserted state of the card receptor, a projection on a lever, actuated through the entry, engages the housing wall within the opening in the telephone station and thereby arrests the card receptor in the read position. The lever thereby projects minimally beyond the outer contours of the telephone station, so that upon completion of the read procedure the card receptor may be drawn from its locked position by downward pressure on the lever.
This card reader has the disadvantage that the card receptor must be drawn, at least partially, out of the telephone station in order to insert and/or remove the card. Aside from the difficulty of inserting and removing the card, this structure makes it possible that the contacts in the card receptor will become contaminated.
It is known to avoid this disadvantage through the use of a longitudinal slide which is movable within a fixed receptor. The slide, which supports the contact apparatus by which the card is read, is mechanically arrested in the read position by a cam or by an electromagnet. This has the disadvantage that the card projects so far out of the card reader in the read position, that it may be removed without unlocking of the slide. (This unlocking may follow, for example, during cam locking, due to renewed pressure on the card, and the resulting release of this spring loaded element.) The contact springs by which the card is read then slide over the sensitive reading area of the card. This eventually damages the card and makes it unusable.
It has therefore been proposed to fix the card in position during reading by using a pin to engage a mating hole in the card. This is undesirable because the card should be universally useable and not limited to use with a specific type of card reader.
It is also known to lock the card during reading by an over-riding hook of a locking lever, so that the card is not removable by the user.
In certain applications it may be desirable to return the card to the user automatically, e.g. after it has been read.
One object of the invention is to further improve existing locking and unlocking devices to make them more user-friendly.